The focal length of a wide-aperture objective lens of the usual operating microscopes is constant, and corresponding working distance and magnification times are certain. As shown in FIG. 1a, when it needs to change the focal length of the wide-aperture lens, it is achieved by switching to a lens Wa or Wb with different focal lengths, and the drawbacks are discontinuous change on the focal length of the objective lens, inconvenient replacement, affecting the use. There is a continuous zoom operating microscope system using a compensating lens moving non-linearly and a lens group moving linearly, which has a complex structure and a complicated process, and belongs to a different type.